OFDM can be embodied through a simple equalizer, and has a characteristic that it is strong against multipath fading and is selected and used for several wireless communication systems such as a wireless local area network (WLAN), a wireless metropolitan area network (WMAN), a digital audio broadcast (DAB) network, and a digital video broadcast (DVB) network.
However, because OFDM use many carrier waves, signals of the same phase are combined and thus a high peak-to-average power ratio (PAPR) occurs, and due to a high PAPR, an operation point of a power amplifier of an OFDM transmitter is positioned at a non-linear area and thus non-linear distortion of a signal occurs. Therefore, in an OFDM system, a power amplifier is backed off to reduce influence of a PAPR, and when enough backoff is not given to the power amplifier, a frequency spectrum of the system is widened and distortion by modulation between mutual frequencies occurs and system performance is resultantly deteriorated.
It is essential to lower the PAPR for power efficiency and down-sizing of an OFDM transmitter, but there is a drawback that when the PAPR is lowered, receiving performance is deteriorated.
Further, in visible light communication (VLC) using OFDM, it is efficient to lower the PAPR to 0 dB, but in a case of optical communication instead of using light such as infrared rays, it is necessary to raise the PAPR for receiving performance. That is, in an OFDM system, when the PAPR can be adjusted according to a receiving environment, performance of the system can be improved.
As a method of lowering the PAPR in the OFDM system, various methods such as a block coding method and a clipping method have been suggested, but these methods cannot lower the PAPR to 0 dB, and it is not allowed to change the PAPR according to a receiving environment.